1. Field of the Invention
The present invention relates generally to light weight composite tubular elements specifically adapted to withstand compressive forces. In particular, the present invention relates to push rods employed in internal combustion engines.
2. Prior Art
Presently, transmitting thrust between a cam shaft and a valve rocker in an internal combustion engine to operate the valve is accomplished by means of a metallic push rod. Metal rods have long since been the material of choice for such devices because of the compressive forces to which the rods are subjected and the inherent elastic stiffness required to preclude buckling failure. Recent emphasis on increasing fuel economy of such internal combustion engines has led to the proposal of replacing numerous parts of such engines by lighter weight materials that are equal in strength and stiffness to the metal components. In U.K. Pat. No. 1,343,983, for example, a push rod having a plastic shank reinforced with carbon fiber and metal thrust transmitting members secured at both ends of the shank is disclosed. All the fibers of the patented push rod are longitudinally oriented. Among the disadvantages of having solely longitudinally oriented reinforcing fibers in such a push rod is the fact that the compressive forces tend to broom the ends of the reinforcing fibers, thereby resulting in shortened life of the rod and that such rods do not provide sufficient shear resistance.